Large numbers of North Korean fishing boats are washing up along the Japanese coast, some of which have contained decaying corpses.

Winds and water currents push dozens of boats onto Japan's northern coasts annually. Rickety North Korean fishing boats are particularly vulnerable because they lack the sturdiness and equipment to return home.

But the alarming pace over the past few weeks has prompted Japanese authorities to step up patrols.

In November of this year alone, 28 of the so-called "ghost ships" were discovered by Japanese authorities with 42 people who claim to be fishermen found alive.